Smart doorbell



FIG. 1 is a top, front, and left side perspective view of a smart doorbell showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof.

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a left side elevational view thereof;

FIG. 6 is a top plan view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is a top, rear, right side perspective view thereof.

The broken lines shown in the drawings depict portions of the smart doorbell that form no part of the claimed design. 

CLAIM The ornamental design for a smart doorbell, as shown and described. 